1. Field of the Invention
The present invention relates to a substrate processing apparatus and method for performing a vacuum process with respect to a substrate such as a semiconductor wafer, a substrate for a liquid crystal display, or an organic EL device.
2. Description of the Related Art
In manufacturing semiconductor devices or FPDs (flat panel displays), various processes such as film formation, etching, oxidation, and dispersion are performed to a semiconductor wafer (hereinafter, referred to as the wafer) or a substrate for a liquid crystal display. In order to perform the above processes with a high throughput, a substrate processing apparatus that is referred to as a multi-chamber system is used.
As shown in FIG. 9, an example of the substrate processing apparatus includes a FOUP holding stage 1 on which a front opening unified pod (FOUP) that is a transport container receiving a plurality of wafers is mounted, a transfer module (TM) 2 having a transfer arm 5 for transferring wafers W and disposed in a vacuum atmosphere, a plurality of process modules (PMs) 3 disposed around the TM 2 and performing predetermined processes with respect to the wafers W under the vacuum atmosphere, a loader module (LM) 4 including a main transfer unit that has a transfer arm for transferring the wafers W and disposed in an atmospheric pressure, two load lock modules (LLMs) 6a and 6b disposed between the LM 4 and the TM 2 and switchable between the vacuum atmosphere and the atmospheric pressure, and an orienter (ORT) (not shown) provided adjacent to the LM 4 for pre-aligning orientation of the wafers W.
In the above substrate processing apparatus, the wafer W is transferred in a following route, for example. The wafer W that is unprocessed and mounted on the FOUP holding stage 1 is transferred in order of the LM 4, the ORT, the LLM 6a, the TM 2, and the PM 3. In addition, after undergoing a process, for example, an etching process, under a predetermined processing gas atmosphere in the PM 3, the processed wafer W is transferred in order of the TM 2, the LLM 6b, the LM 4, and the FOUP holding stage 1.
Recently, a problem has occurred, that is, for some kind of the processing gas, when the processed wafer W returns to the LM 4, the wafer W reacts with moisture in the air, and then discharges a corrosive gas to the vicinity thereof. In addition, in some case, since the reaction for generating the corrosive gas lasts for a predetermined time, the corrosive gas contaminates the unprocessed wafers W in the FOUP to which the processed wafer returns. For example, in the PM 3, a processing gas, for example, HBr gas or Cl2 gas, may be plasmatized for etching a polysilicon film formed on the wafer W. In this case, products (silicon bromide or silicon chloride) accompanied with the etching process remain on the wafer W. Recently, since line widths of patterns of the wafer W have been reduced due to a fine design rule of the wafer W, by-products are more likely to remain between structures formed on the wafer W. When the wafer W is transferred to the LM 4 that is under the atmospheric pressure, the silicon bromide or silicon chloride reacts with the moisture in the air to generate the corrosive gas such as hydrogen bromide or hydrogen chloride, and then scatters. In addition, the corrosive gas reacts with a very small amount of ammonia that exists in the air, so that particles such as ammonium bromide or ammonium chloride are generated and dispersed in the LM 4.
To address the above problems, as shown in FIG. 9, a purge storage 7 is provided in the substrate processing apparatus in order to temporarily store the processed wafer W under the atmospheric pressure. The corrosive gas that is generated by the reaction of the processed wafer W with the air may be removed in the purge storage 7, and thus, discharge of the corrosive gas from the wafer W that returns to the FOUP can be prevented.
However, when the processed wafer W is transferred from the LLM 6b to the purge storage 7, the wafer W passes through the LM 4. Since the LM 4 is a chamber that transfers the wafer W under the atmospheric pressure, the wafer W may discharge the corrosive gas on entering the LM 4. Therefore, a metal portion of the LM 4, for example, a wall portion of a transfer chamber or a transfer unit may be corroded, and the corroded portion may cause metal contamination due to friction caused by a movement of a machine, for example. In order to prevent the corrosion and the metal contamination, large-scale countermeasures against the corrosion are performed, for example, reinforced exhaustion, surface process of the wall portion in the transfer chamber (Teflon™) coating or alumite processing), and selection of a corrosion-resistant material.
However, the large-scale countermeasures against the corrosion increase costs of the LM. Recently, since the substrate processing apparatus is requested to have low costs, improved reliability, reinforced safety, and reduced maintenance costs, the LM that may not require, or may reduce, the countermeasures against the corrosion has been required. In order to reduce the influence of the corrosive gas on the LM, Patent Document 1 discloses a substrate processing apparatus, in which the purge storage is disposed to be adjacent to the load lock module so that the processed substrate is transferred from the load lock module to the purge storage by a main transfer unit of the loader module.    (Patent Document 1) Japanese Laid-open Patent Publication No. 2008-53550
However, in the substrate processing apparatus disclosed in Patent Document 1, a part of the main transfer unit (for example, a transferring arm unit that transfers the wafer) may contact the corrosive gas, and the corrosive gas generated in the purge storage may flow into the loader module. Thus, the countermeasures against the corrosion disclosed in Patent Document 1 cannot completely prevent the corrosion. Moreover, one main transfer unit disposed on the loader module performs both of the transferring of the wafer from the load lock module to the purge storage and the returning of the wafer from the purge storage to the FOUP holding stage, and thus, a throughput of the substrate processing apparatus is reduced.